"I was pretty confident the book would be big, but not this big," said John Grogan, the book's author and Marley's owner, sitting in his large brick house surrounded by fields and woods in rural Pennsylvania. So far, "Marley & Me," published by William Morrow in November, has sold close to 500,000 copies. It is now in its 20th printing, with 870,000 books in print, the publisher said.

As readers of the book know, Marley is dead, but as Mr. Grogan, a columnist for The Philadelphia Inquirer, said, "Marley's ghost is everywhere."

"Here, he was locked in here," he said, opening the basement door. He pointed to where Marley had scraped at the wall with his claws and gnawed at the door frame trying to escape. "The wood door frame was totally gone to the studs," Mr. Grogan said. ("He was an obnoxious greeter of guests," he explained later. "For the sake of our company, unless they were really, really good friends, we would lock him there so they could come over without being slobbered on.")

Marley was, in a way, a dog who loved too much. He would hurl himself through screen doors to get to Mr. Grogan or his wife, Jenny Vogt. When they locked him in a metal dog crate, he separated the steel bars.

"It looked like the Jaws of Life had pulled it open," Mr. Grogan said. Marley flung drool on guests. He stole Ms. Vogt's underwear. He ate her jewelry. Thunderstorms gave him anxiety attacks, and then he would chew through things, mattresses, the couch.

But "Marley & Me" is not just a book about a dog. In fact, it is a love story, of Mr. Grogan and his wife, a young married couple contemplating having a family. "We were young," the book begins, irresistibly. "We were in love." Ms. Vogt was nervous about caring for a baby and thought a dog "would be good practice," Mr. Grogan writes. A breeder offered them a discount on a puppy. "The little guy's on clearance," Ms. Vogt begged her husband as Marley somersaulted into their laps, gnawed on their fingers and clawed his way up to lick their faces.

An error has occurred. Please try again later.

You are already subscribed to this email.

The book follows the couple through their efforts to have a child. When Ms. Vogt suffered a miscarriage, Marley seemed to mourn with her.

"His tail hung flat between his legs," Mr. Grogan writes, "the first time I could remember it not wagging whenever he was touching one of us. His eyes were turned up at her, and he whimpered softly."

When their three children did arrive, he became their guardian, delicately licking their faces and ears, allowing them to crawl all over him. The problem, Mr. Grogan writes, was not keeping Marley from hurting one of the babies, but keeping him out of the diaper pail.

After Marley died in 2003, Mr. Grogan wrote a column about him for The Inquirer and was stunned when he got 800 responses from other dog owners. He thought Marley's story might make a book and wrote a proposal; the final manuscript was sold to Morrow for $200,000.

Lisa Gallagher, William Morrow's publisher, said she began to suspect the book would do well when she noticed staff members passing it around among themselves. Morrow printed nearly 6,000 readers editions and sent them to booksellers. It also gave away copies at last June's BookExpo America, the industry trade show, in New York. In a nod to the book's tearjerker qualities, the company distributed tissue with Marley's image on it at regional bookseller meetings; it also sent Frisbees with the book's title on them to stores.

Dan Mayer, who buys pet books for Barnes & Noble, was enthusiastic about the book because, he said, it is "more of a memoir." And then there's the book's cover, a photograph of Marley as a puppy looking appealingly up at the reader. "It's really hard to walk past the cover of this book and not want to pick it up," Mr. Mayer said. Barnes & Noble chose "Marley" for its Discover program, which earns a book prominent display space in the company's stores and on its Web site, reviews in in-store brochures and often priority for advertising and author readings.

Of course, a large part of the book's appeal is that Marley was a very, very bad dog. And the book is a lesson in unconditional love. The Grogans tried obedience school, but Marley was expelled. They sent him again, and this time he came in seventh in a class of eight. The dog behind him was "a psychopathic pit bull," Mr. Grogan writes. Marley ate his own obedience certificate.

These days, Marley lies buried in an unmarked grave in the garden at the edge of the woods. The Grogans now have a successor, Gracie, who is 18 months old. She is a female Lab. Like all Labs, she is exuberant and high-spirited.

"But what she has is what Marley didn't have," Mr. Grogan said, "the ability to calm down."

"We call her the anti-Marley," Mr. Grogan said.

A version of this article appears in print on , on Page B1 of the National edition with the headline: Belatedly, a Bad Dog Finds His Forte: Selling Books. Order Reprints|Today's Paper|Subscribe